The present invention relates to a backlight unit to be applied in a liquid crystal display apparatus having a liquid crystal panel, and it relates to, in particular, a backlight unit of thin-type, having high luminance and being high in uniformity of luminance thereof, and also being suitable to be applied therein a technology for controlling an intensity of lights upon a liquid crystal panel for each of a plural number of regions, individually (hereinafter, such technology will be called, “an area or local dimming”), and a video display apparatus applying the same therein.
In recent years, as a backlight unit for the liquid crystal display apparatus is applied one of a side light method, sometimes, disposing light source(s) on one end of a liquid crystal panel or both ends thereof to irradiate lights upon the liquid crystal panel. The side light method is advantageous for thin-sizing of the apparatus, but since the light sources are disposed concentrating on the end(s) of the apparatus, heats generated from the light source(s) are also concentrated on the end of the apparatus, and therefore it is difficult to radiate the heats. And, application of the area or local dimming is also difficult, and large-sizing of the apparatus is also difficult. As the conventional art of such side light method is already known what is disclosed in the following Patent Document 1, for example.
On the other hand, so-called a just-under method, building up the backlight by aligning a large number of lines of the light sources on a rear surface of the liquid crystal, is disadvantageous for thin-sizing, since it is necessary to enlarge the distance between the liquid crystal panel and the light source, up to a certain degree so that the lights irradiate upon an entire surface of the liquid crystal panel equally. Also, if trying to build the apparatus of the just-under method to be thin, it is necessary to increase a number of the light sources, and this rises up the const and the power consumption thereof. As the conventional art of such just-under method is already known what is disclosed in the following Patent Document 2, for example.    [Patent Document 1] Japanese Patent Laying-Open No. 2008-103162 (2008); and    [Patent Document 2] Japanese Patent Laying-Open No. 2008-103200 (2008).